This invention relates to a process for polymerizing olefins. The process is performed in the presence of a supported indenoindolyl-containing catalyst system and an organoboron or organoaluminum-treated solid. The presence of the organoboron or organoaluminum-treated solid surprisingly leads to an increased activity compared to polymerization processes performed without it.
Many olefin polymerization catalysts are known, including conventional Ziegler-Natta catalysts. While these catalysts are inexpensive, they exhibit low activity, produce polymers having narrow to medium molecular weight distributions (Mw/Mn greater than 4), and are generally poor at incorporating xcex1-olefin comonomers. To improve polymer properties, highly active single-site catalysts, in particular metallocenes, are beginning to replace Ziegler-Natta catalysts. Although more expensive, the new catalysts give polymers with narrow molecular weight distributions, and good comonomer incorporation, which allows easier production of low-density polymers. One disadvantage of metallocene catalysts is that they tend to produce lower molecular weight polymers at higher temperatures.
Recent attention has focused on developing improved single-site catalysts in which a cyclopentadienyl ring ligand is replaced by a heteroatomic ring ligand. These catalysts may be referred to generally as xe2x80x9cheterometallocenes.xe2x80x9d One particular type of heterometallocene of interest contains an indenoindolyl ligand as disclosed in U.S. Pat. No. 6,232,260 and PCT Int. Appl. WO 99/24446.
Single-site catalysts are typically soluble in the polymerization reaction medium and are therefore valuable for solution processes. However, for gas-phase, slurry, and bulk monomer processes, it is useful to immobilize the catalyst on a carrier or support in order to control polymer morphology. U.S. Pat. No. 6,211,311 teaches support chemical pretreatment for supported single-site catalysts that contain a polymerization-stable heteroatomic ligand. For catalysts containing indenoindolyl ligands, both U.S. Pat. No. 6,232,260 and PCT Int. Appl. WO 99/24446 disclose that a support such as silica or alumina can be used. Increasing the activity of the polymerization process is an important objective in order to achieve an economical process. As with any chemical process, it is desirable to develop new polymerization methods and catalysts.
In sum, new olefin polymerization processes using supported indenoindolyl-containing catalysts are needed. Particularly valuable processes would have improved catalyst activity.
The invention is a process for polymerizing olefins. The process is performed in the presence of a supported indenoindolyl-containing catalyst system and an organoboron or organoaluminum-treated solid. The supported indenoindolyl catalyst system comprises a support, an organometallic complex comprising a Group 3 to 10 transition or lanthanide metal, M, and at least one indenoindolyl ligand that is xcfx80-bonded to M, and an activator. The presence of the organoboron or organoaluminum-treated solid surprisingly leads to an increased activity compared to polymerization processes that do not use the treated solid. In addition, the presence of the treated solid enhances catalyst operability by reducing the incidence of reactor fouling.
The process of the invention comprises polymerizing one or more olefins in the presence of a supported indenoindolyl catalyst system. Supported indenoindolyl-containing catalyst systems include an indenoindolyl-containing complex, an activator, and a support.
The supported catalyst system of the invention contains an organometallic complex comprising a Group 3 to 10 transition or lanthanide metal, M, and at least one indenoindolyl ligand that is xcfx80-bonded to M. The metal, M, may be any Group 3 to 10 transition or lanthanide metal. Preferably, the catalyst contains a Group 4 to 6 transition metal; more preferably, the catalyst contains a Group 4 metal such as titanium or zirconium.
The organometallic complex of the invention also contains at least one indenoindolyl ligand that is xcfx80-bonded to M. Indenoindolyl ligands are well-known in the art and are taught in U.S. Pat. No. 6,232,260, the teachings of which are incorporated herein by reference. The indenoindolyl ligand is an anionic ligand derived from an indenoindole. An indenoindole is an organic compound that has both indole and indene rings. The five-membered rings from each are fused, i.e., they share two or more carbon atoms. Any of the indenoindolyl ring atoms can be unsubstituted or substituted with one or more groups such as alkyl, aryl, aralkyl, halogen, silyl, nitro, dialkylamino, diarylamino, alkoxy, aryloxy, thioether, or the like. Additional rings can be present, as long as an indenoindole moiety is present.
Suitable indenoindole ligand precursors include, for example, 5,10-dihydroindeno[3,2-b]indole, 4,8,10-trimethyl-5H-indeno[3,2-b]indole, 4-tert-butyl-8-methyl-5,10-dihydroindeno[3,2-b]indole, 4,8-dichloro-5,10-dihydroindeno[3,2-b]indole, 10-methylbenzo[f]-5H-indeno[3,2-b]indole, benzo[g]-5,10-dihydroindeno[3,2-b]indole, 5,10-dihydroindeno[3,2-b]benzo[e]indole, benzo[g]-5,10-dihydroindeno[3,2-b]benzo[e]indole, and the like.
The indenoindolyl ligand is generated by deprotonating a ligand precursor with a base to give an anionic ring system with a high degree of aromaticity (highly delocalized). Reaction of the anion with, e.g., a transition metal halide gives the desired organometallic complex. The indenoindolyl ligand is xcfx80-bonded to M in the complex.
The organometallic complex optionally includes one or more additional polymerization-stable, anionic ligands. Examples include substituted and unsubstituted cyclopentadienyl, fluorenyl, and indenyl, or the like, such as those described in U.S. Pat. Nos. 4,791,180 and 4,752,597, the teachings of which are incorporated herein by reference. Suitable ligands also include substituted and unsubstituted boraaryl, pyrrolyl, indolyl, quinolinyl, pyridinyl, and azaborolinyl as described in U.S. Pat. Nos. 5,554,775, 5,539,124, 5,637,660, and 5,902,866, the teachings of which are also incorporated herein by reference. The organometallic complex also usually includes one or more labile ligands such as halides, alkoxys, siloxys, alkyls, alkaryls, aryls, dialkylaminos, or the like. Particularly preferred are halides, alkyls, and alkaryls (e.g., chloride, methyl, benzyl).
The indenoindolyl and/or polymerization-stable ligands can be bridged. Groups that can be used to bridge the ligands include, for example, methylene, ethylene, 1,2-phenylene, dialkylsilyls, and diarylsilyls. Normally, only a single bridge is included, but complexes with two bridging groups can be used. Bridging the ligand changes the geometry around the transition metal and can improve catalyst activity and other properties, such as molecular weight, comonomer incorporation, and thermal stability.
Suitable activators include alumoxanes. Preferred alumoxanes are polymeric aluminum compounds represented by the cyclic formula (R1xe2x80x94Alxe2x80x94O)s or the linear formula R1(R1xe2x80x94Alxe2x80x94O)sAlR1 wherein R1 is a C1-C5 alkyl group and s is an integer from 1 to about 20. Preferably, R1 is methyl and s is from about 4 to about 20. Exemplary alumoxane activators are (poly)methylalumoxane (MAO), ethylalumoxane, and diisobutylalumoxane. Optionally, the activator is a trialkyl or triaryl aluminum compound, which preferably has the formula AlR23 where R2 denotes a C1-C20 hydrocarbyl.
Suitable activators also include substituted or unsubstituted trialkyl or triaryl boron derivatives, such as tris(perfluorophenyl)boron, and ionic borates such as tri(n-butyl)ammonium tetrakis(pentafluorophenyl) boron or trityl tetrakis(pentafluorophenyl) boron. The ionic borates ionize the neutral organometallic compound to produce an active catalyst for olefin polymerization. See, for instance, U.S. Pat. Nos. 5,153,157, 5,198,401, and 5,241,025, all of which are incorporated herein by reference. Suitable activators may be combined or used separately.
The molar ratio of the metal of the activator component to the transition metal of the single-site catalyst is preferably in the range of about 0.3:1 to 1000:1, more preferably from about 20:1 to 800:1, and most preferably from about 30:1 to 500:1. Where the activator is an ionic borate, the molar ratio of the metal of the activator component to the transition metal of the single-site catalyst is preferably in the range of about 0.3:1 to 8:1.
The organometallic complex is immobilized on a support, which is preferably a porous material. The support can be inorganic oxides, inorganic chlorides, and organic polymer resins, or mixtures thereof. Preferred inorganic oxides include oxides of Group 2, 3, 4, 5, 13, or 14 elements. Preferred inorganic chlorides include chlorides of the Group 2 elements. Preferred organic polymer resins include polystyrene, styrene-divinylbenzene copolymers, and polybenzimidizole. Particularly preferred supports include silica, alumina, silica-aluminas, magnesias, titania, zirconia, magnesium chloride, and polystyrene. Silica is most preferred.
Preferably, the support has a surface area in the range of about 10 to about 1000 m2/g, more preferably from about 50 to about 800 m2/g, and most preferably from about 100 to about 700 m2/g. Preferably, the pore volume of the support is in the range of about 0.1 to about 5.0 mL/g, more preferably from about 0.5 to about 4.0 mL/g, and most preferably from about 0.8 to about 3.5 mL/g. The average pore diameter is typically in the range of about 10 to about 1000 xc3x85, preferably about 15 to about 500 xc3x85, and most preferably about 20 to about 350 xc3x85.
The organometallic complex is supported using any of a variety of immobilization techniques. In one method, the organometallic complex is dissolved in a solvent and combined with the support. Evaporation of the solvent gives a supported catalyst. An incipient wetness method can also be used. The activator can also be deposited on the support or it can be introduced into the reactor separately from the catalyst.
The support can be used without any pre-treatment prior to immobilization of the organometallic compound and activator, but a support pre-treatment step is preferred. The support may be calcined and/or modified by a chemical additive. If the support is pre-treated by calcination, the calcination temperature is preferably greater than 150xc2x0 C. The chemical additives that may be used to pre-treat the support include organoaluminums, organoboranes, organomagnesiums, organosilanes, and organozinc compounds. Preferred chemical additives include alumoxanes, hexamethyldisilazane, trimethylchlorosilane, Grignard reagents, and triethylboron. Support modification techniques are taught in U.S. Pat. Nos. 4,508,843, 4,530,913, and 4,565,795, the teachings of which are incorporated herein by reference.
The process of the invention is also performed in the presence an organoboron or organoaluminum-treated solid. The organoboron or organoaluminum-treated solid is prepared by treating an inorganic solid or an organic polymer solid with an organoboron or an organoaluminum compound.
Suitable organoaluminum compounds include alumoxanes, alkyl aluminums, and alkyl aluminum halides. Suitable alumoxanes include polymeric aluminum compounds represented by the cyclic formula (R3xe2x80x94Alxe2x80x94O)s or the linear formula R3(R3xe2x80x94Alxe2x80x94O)sAlR3 wherein R3 is a C1-C5 alkyl group and s is an integer from 1 to about 20. Preferably, R3 is methyl and s is from about 4 to about 20. Exemplary alumoxane activators are (poly)methylalumoxane (MAO), ethylalumoxane, and diisobutylalumoxane.
Preferred alkyl aluminums include trialkyl or triaryl aluminum compound, which preferably has the formula AlR4R5R6 where R4, R5, and R6 denote the same or different C1-C20 hydrocarbyl. Particularly preferred alkyl aluminums are trimethylaluminum, triethylaluminum, tripropylaluminum, and triisobutylaluminum.
Suitable alkyl aluminum halides include dialkyl aluminum halide and alkyl aluminum dihalide compounds, which preferably have the formula AlR4R5 or AlR4X2 where X is Cl, Br, or I. Exemplary alkyl aluminum halides are dimethylaluminum chloride, methylaluminum dichloride, diethylaluminum chloride, ethylaluminum dichloride, diisobutylaluminum chloride and isobutylaluminum dichloride.
Preferred organoboron compounds include alkyl, aryl, and alkoxy boron compounds. More prefered organoboron compounds are trialkylborons, triarylborons, and trialkoxyborons having the formula R4R5R6B or B(OR4)(OR5)(OR6). Most preferred are trimethylboron, triethylboron, tripropylboron, triisobutylboron, trimethoxyboron, triethoxyboron, tripropoxyboron, and triphenoxyboron.
The solid is an inorganic solid or an organic polymer solid, and can be inorganic oxides, inorganic chlorides, and organic polymer resins, or mixtures thereof. Preferred inorganic oxides include oxides of Group 2, 3, 4, 5, 13, or 14 elements. Preferred inorganic chlorides include chlorides of the Group 2 elements. Preferred organic polymer resins include polystyrene, styrene-divinylbenzene copolymers, and polybenzimidizole. Particularly preferred solids include silica, alumina, silica-aluminas, magnesias, titania, zirconia, magnesium chloride, and polystyrene. Silica is most preferred.
Preferably, the solid has a surface area in the range of about 10 to about 1000 m2/g, more preferably from about 50 to about 800 m2/g, and most preferably from about 100 to about 700 m2/g. Preferably, the pore volume of the support is in the range of about 0.1 to about 5.0 mL/g, more preferably from about 0.5 to about 4.0 mL/g, and most preferably from about 0.8 to about 3.5 mL/g. The average pore diameter is typically in the range of about 10 to about 1000 xc3x85, preferably about 15 to about 500 xc3x85, and most preferably about 20 to about 350 xc3x85.
The organoboron or organoaluminum modifier is added to the solid in an amount preferably in the range of about 0.1 to 20 mmoles of aluminum or boron (contained in the modifier) per gram of solid, more preferably from about 0.2 to 10 mmoles/gram, and most preferably from about 0.5 to 5 mmoles/gram. Treatment with organoboron or organoaluminum modifier is typically performed in the liquid phase, and the organoboron or organoaluminum modifier is applied to the solid as a liquid, either by itself or as a solution in a suitable solvent such as a hydrocarbon. An incipient wetness method or gas-phase impregnation may also be used to treat the solid.
The solid is preferably heated at a temperature from about 50xc2x0 C. to about 1000xc2x0 C., more preferably from about 100xc2x0 C. to about 800xc2x0 C., before and/or after the organoboron or organoaluminum modification. After organoboron or organoaluminum modification, the solid is most preferably dried in vacuum at a temperature from about 20xc2x0 C. to about 120xc2x0 C.
The process of the invention is used to polymerize olefins, preferably xcex1-olefins. Suitable olefins include, for example, propylene, 1-butene, 1-hexene, 1-octene, ethylene and the like, and mixtures thereof. The catalyst is valuable for copolymerizing ethylene with xcex1-olefins or di-olefins (e.g., 1,3-butadiene, 1,4-hexadiene, 1,5-hexadiene).
Processes of the invention include liquid phase (slurry, solution, suspension, bulk), high-pressure fluid phase, or gas phase polymerization processes, or a combination of these. The pressure in the polymerization reaction zones typically ranges from about 15 psia to about 30,000 psia, and the temperature usually ranges from about xe2x88x92100xc2x0 C. to about 300xc2x0 C.
Surprisingly, olefin polymerization using a supported indenoindolyl catalyst results in significantly higher activity and improved operability when performed in the presence of an organoboron or organoaluminum-treated solid (see Table 1). Polymer properties, including density, remain unchanged.
The following examples merely illustrate the invention. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.